class SolutionBuildTreeByPreAndIno {

    static class TreeNode {
        public int val;
        public TreeNode left;
        public TreeNode right;

        public TreeNode(int val) {
            this.val = val;
        }
    }

    int preIndex = 0;
    public TreeNode buildTree(int[] preorder, int[] inorder) {
        
        return buildTreeChild(preorder,inorder,0,inorder.length-1);
    }
    public TreeNode buildTreeChild(int[] preorder, int[] inorder,int inbegin,int inend) {
        if(inbegin > inend) {
            return null;
        }
        TreeNode root = new TreeNode(preorder[preIndex]);

        int rootIndex = findRootIndex(inorder,inbegin,inend,preorder[preIndex]);
        preIndex++;

        root.left = buildTreeChild(preorder,inorder,inbegin,rootIndex-1);

        root.right = buildTreeChild(preorder,inorder,rootIndex+1,inend);

        return root;
    }

    private int findRootIndex(int[] inorder,int inbegin,int inend,int key) {
        for(int i = inbegin;i <= inend;i++ ) {
            if(inorder[i] == key) {
                return i;
            }
        }
        return -1;
    }


}